Nickel-mediated rearrangements

In 1974, Paul Gassman and co-workers recognized the potential of the described rearrangement and reported a one-pot, general method for the synthesis of indoles based on the rearrangement of the nonisolable aza-sulfonium ylides. In the very first example of this method, aniline 4 was treated sequentially with f-BuOCl, methylthio-2-propanone 5 and triethylamine to provide methylthioindole 6 in 69% yield. Raney-nickel-mediated desulfuriza-tion afforded 2-methylindole 7 in 79% yield. 

In the synthesis of a-amino acids [290] through addition of the carbanion of MMTS to nitriles the overall process involves three other steps frequently encountered in sulfur-mediated chemistry a Pummerer-type rearrangement, with a less common migration of a methylthio group, and a Raney nickel desulfurization following transesterification of the thioester function. 

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